In investment casting, a disposable or consumable pattern is formed in the shape of the component to be cast. The pattern is then coated in a ceramic, which sets to form a mould. The pattern is then removed from the mould, by melting or chemical leaching (dissolving) to leave a void in the mould, in the shape of the component to be cast. Molten metal is poured into the void, through the same opening that the pattern is removed through. The molten metal adopts the shape of the void, and hence the shape of the component to be formed. Once the metal is solidified, the mould is broken to remove the component.
When making complex components by investment casting, the pattern may be formed in several parts, which have to be joined together. Typically, with patterns made of wax, the joint between parts is formed by melting the mating faces of the surfaces together, and using a hot knife to form stitching lines.